CRYSTAL-STRUCTURE OF A LUMINESCENT EUROPIUM(III) COMPLEX - PROBING THE ACTIVE SPECIES IN DISSOCIATION-ENHANCED LANTHANIDE FLUOROIMMUNOASSAY

The highly luminescent complex [Eu(fnac)2(topo)2(NO3)], which contains the two component ligands [fnac, the anion of 4,4,4-trifluoro-1-(2-na phthyl)butane-1,3-dione, and topo, trioctylphosphine oxide] of the lum inescent species in the dissociation-enhanced lanthanide fluoroimmunoa ssay method, has been prepared and defined by an X-ray crystal structu re analysis. The complex crystallizes in the Ccmm space group, a 17.06 4(18), b 30.254(21) and c 16.391(4) angstrom, Z = 4, and a single-crys tal X-ray structure determination refined to R 0.056 for 1772 independ ent 'observed' reflections. The complex exhibits a dodecahedral EuO8 s tructure with bidentate nitrate ion [Eu-O 2.512(10) angstrom}, two bid entate substituted acetylacetonate (fnac) [Eu-O 2.379(9), 2.400(9) ang strom], and two monodentate long-chain phospine oxide (topo) ligands [ Eu-O 2-295(9) angstrom].